The present invention relates to an apparatus and a method for manufacturing a thick-walled bent pipe.
As for a metal elbow for piping, those with an elbow body 111 being attached to a piping block 113 or the like with a fastening nut 112 as shown in FIG. 11 is used conventionally. Both ends of the elbow body 111 are threaded, and one thread is screwed into the piping block 113 or the like and fastened with the nut 112, while a pipe not shown is attached to the other thread. The elbow body 111 can be freely oriented to the piping and fixed by being fastened with the nut 112. The elbow body 111 is provided with parallel plane portions 111s and 111s so that the elbow body 111 can be fixed with a spanner or the like when it is attached. Further, the elbow body 111 is bent at substantially 90 degrees, which reduces the protruding amount from the piping block 113 or the like, thus requiring less piping space.
In a section of the elbow body 111, two fluid paths 111d and 111d cross each other at substantially 90 degrees as shown in FIG. 12. Further, since the elbow needs to be threaded, a margin to cut needs to be secured, which makes a material for the elbow thick-walled. In addition, it is necessary to secure pressure resistance of an elbow in order to respond to high-pressurization of the fluid devices in recent years, and the wall thickness of the elbow body 111 after being worked becomes larger.
Accordingly, it is difficult to manufacture the elbow body 111 as shown in FIG. 12 by bending a thick-walled metal pipe at a small radius, because the pipe is crushed or the wall thickness of the pipe is reduced. Consequently, a material of the elbow is made by cutting out a thick metal plate and forming it into a right-angle elbow, then the material is drilled from both sides thereof to make the fluid paths 111d and 111d crossing each other at substantially 90 degrees, and thereafter screw thread cutting is performed for both ends to thereby manufacture the elbow body 111.
However, in the above manufacturing method, the process of cutting the material includes two drilling operations and two screw thread cutting operations, which results in too many working steps, and thus the number of steps of preparing the material is large. Further, in the drilling work, burrs caused by the drilling work occur at a crossing portion of the fluid paths 111d and 111d crossing each other at substantially 90 degrees. Thus, an operation of removing the burrs has to be performed, and the deburring operation is not easy and takes time, since burrs in the inner parts of small holes have to be removed. Further, many cutting operations increase cutting amount of the material, thus reducing yields. Consequently, manufacturing cost is increased.
As a solution to the above disadvantages, an apparatus for manufacturing a thick-walled bent pipe described in Japanese Patent Application Laid-open No. 2000-343136 is proposed. This apparatus includes an upper die 210 having a presser die 212 and an upper guide 211 having a guide surface 211a in a circular arc form for guiding a pair of lower dies 221 and 222, as shown in FIG. 10. The apparatus also includes a pair of lower dies 221 and 222 having sliding plane 220c and 220c in a circular arc form, and a lower guide 230 having sliding planes 230a and 230a for mounting a pair of the lower dies 221 and 222 thereon. In connection with a descent of the upper die 210, the sliding planes 220c and 220c in the circular arc form of a pair of lower dies 221 and 222 abut to and slide along the guide surface 211a in the circular arc form of the upper guide 211 of the upper die 210. At the same time as this, lower end portions 220f and 220f of a pair of the lower dies 221 and 221 abut to and slide along the sliding planes 230a and 230a of the lower guide 230. Sliding in this manner makes the structure in which a pair of the blower dies 221 and 222 are respectively rotatable opposite to each other.
According to this apparatus, a pair of the lower dies 221 and 222 rotate along the guide surface 211a in the circular arc form of the upper die 210, having a center of rotation O1 while they are facing to each other. Thereby, changes in the distances between both the end surfaces of the thick-walled pipe material 111a and the center O1 of rotation at the start of bending and at the completion of bending are reduced, thus making it possible to form a thick-walled elbow material that is a thick-walled bent pipe with less variations in size.
As a result, the thick-walled pipe can be cut and used as an elbow material, thus making it unnecessary to prepare a forged material. Further, since a thick-walled pipe can be used, drilling for making slender holes to form fluid passages is unnecessary. Further, deburring at the crossing portion of the drilled holes, which is conventionally performed, is made unnecessary. Furthermore, since the thick-walled pipe is round in the outer shape, the margin to cut for screw thread cutting is reduced. Accordingly, a special drill is not needed, drilling work and deburring work are not needed, and cutting amount for screw threading work is reduced, whereby the time required for work, and tool cost can be substantially reduced, and the yield of the material can be improved.
However, since the upper guide 211 of this apparatus has the guide surface 211a in the circular arc form, the guide surface 211a in the circular arc form has to be worked by cutting a block to produce the upper guide 211, which requires a large amount of work and makes the work complicated, and as a result, work cost becomes high. Since the upper guide 211 is in a block form, it has heavy weight, which is inconvenient in handling. Further, the sliding surfaces 220c and 220c in the circular arc form of a pair of the lower dies 221 and 222 abut to and slide along the guide surfaces 211a in the circular arc form of the upper guide 211 of the upper die 210, and thus the sliding surfaces 220c and 220c and the guide surfaces 211a in the circular form are worn or seize if they are used for a long period of time.
The present invention is made in view of the above-described disadvantages, and its object is to provide an apparatus for manufacturing a thick-walled bent pipe with a simple structure at low manufacture cost, which has durability and is capable of manufacturing an elbow material for piping with higher size accuracy with use of a thick-walled pipe material, and a method of manufacturing a thick-walled bent pipe with use of the manufacturing apparatus.
In order to attain the above object, the apparatus for manufacturing a thick-walled bent pipe according to the present invention is an apparatus for manufacturing a thick-walled bent pipe comprising a presser die and a lower die, and has the constitution in which
the lower die comprises a pair of bottom dies having meshing means and
a pair of the bottom dies are allowed to rotate opposite to each other by meshing means, in connection with a descent of the presser die.
According to the above constitution, the apparatus for manufacturing a thick-walled bent pipe has a simple structure, and therefore it has durability at low production cost. In addition, it can manufacture thick-walled elbow materials with high size accuracy.
Further, in the apparatus for manufacturing the thick-walled bent pipe,
a pair of the bottom dies may be provided with stoppers abutting to both end surfaces in a longitudinal direction of a material to be formed.
According to the above constitution, bending work is performed with the thick-walled pipe material being restrained so as to have a set length by the presser die, the lower die and the stoppers of the lower die, thus making it possible to form a thick-walled elbow material of an accurate size.
The apparatus for manufacturing the thick-walled bent pipe may further comprise
side press devices for pressing side surfaces of a material to be formed.
According to the above constitution, the side press devices press the side surfaces of the thick-walled pipe material, and therefore flat surface portions to which a wrench can be applied can be formed on both sides of a center portion of the thick-walled pipe material.
The method for manufacturing a thick-walled bent pipe according to the present invention is a method for
manufacturing a thick-walled bent pipe comprising the steps of placing a thick-walled metal pipe material of a predetermined length on a lower die comprising a pair of bottom dies having meshing means, and
pressing a middle portion in a longitudinal direction of the thick-walled metal pipe material by lowering a presser die, and thereby rotating a pair of the bottom dies opposite to each other by the meshing means to form a thick-walled elbow material of a predetermine size.
According to the above constitution, since the manufacturing apparatus having durability with a simple structure at low production cost is used, and thus a thick-walled elbow material with high size accuracy with use of a thick-walled pipe material can be manufactured at lower cost.
Further, the method for manufacturing the thick-walled bent pipe may further comprises the step of
on pressing the middle portion in the longitudinal direction of the thick-walled metal pipe material, making stoppers provided at a pair of the bottom dies abut to both end surfaces in the longitudinal direction of the thick-walled metal pipe material to restrain both the end surfaces in the longitudinal direction of the thick-walled metal pipe material.
According to the above constitution, the thick-walled pipe material is restrained and bent so as to be in a set size by the presser die, the lower die and the stoppers of the lower die, and thus a thick-walled elbow material of an accurate size can be formed.